Traditional completion methods in cased holes call for running in casing with a cementing shoe at the lower end. After a section of casing is properly located and supported, cement is pumped through it and out the cementing shoe and into an annular space between the casing and the borehole wall. The residual cement is pushed toward the shoe with a dart or a plug to clear the casing interior of excess cement. After the cement sets a perforating gun is placed at the proper depth and fired through the casing and cement for access to the formation behind for production of the well. Alternatively, a section of the casing and the cement behind it can be cut and milled away to provide comparable access to the formation. As an alternative to cementing the casing, the annular space around the casing can be sealed with external casing packers. However, even when using this technique, access to the formation is still required such as by using these aforementioned techniques.
Perforating is a costly operation and has, associated with it the additional hazard of handling explosives. The setting off of perforating guns generates a fair amount of debris in the casing that must be removed. There are also potential adverse effects on the formation from the act of perforation. Traditional cement completions also have potential problems with cement bonding and may require the use of external casing packers for zone isolation between or among various zones in the wellbore.
More recently, expansion of tubulars downhole has become more prevalent. In the past, when expanding a tubular to act as a perforated liner, it has been known to put rectangular slots in the tubular before expanding it. The presence of these open slots weakens the tubular to reduce the effort required to expand it. The open rectangular slots turn into diamond shapes after expansion. An example of this process is U.S. Pat. No. 5,366,012.
Other applications have involved taking screen or slotted liner with rectangular slots and adding covers so that killing the well is not necessary for running in the casing because the casing, in the run in condition will withstand pressure differentials of 50 bar with the blow out preventer closed. After the liner is in position, it is expanded and can function as a slotted liner particularly in unconsolidated formations. This technique is illustrated in U.S. Pat. No. 6,523,611.
In other applications, casing has been outfitted with sliding sleeve valves that selectively cover a plurality of telescoping outlets covered by a rupture disc. When pressure is built up after the sliding sleeve valve is opened, the outlet telescopes through the cement and fractures the formation. Production is then obtained through the telescoping outlets. An example of such a system is U.S. Pat. No. 5,425,424. This system is expensive and has a variety of operational issues of actually breaking all the rupture discs and actually penetrating the formation with the telescoping outlets depending on the wellbore shape.
What is needed and not provided with the prior designs is a system that can eliminate the costly and more risky techniques of perforating or section milling and allow good zone isolation while providing reliable access to the producing formation. These and other advantages of the present invention will become more apparent to those skilled in the art from a review of the description of the preferred embodiment, the drawings and the claims, which appear below.